1. Field of the Invention
The present invention relates to a lithographic apparatus, an array of individually controllable elements and a method for manufacturing a device.
2. Related Art
A lithographic apparatus is a machine that applies a desired pattern onto a substrate or part of a substrate. A lithographic apparatus can be used, for example, in the manufacture of flat panel displays, integrated circuits (ICs) and other devices involving fine structures. In a conventional apparatus, a patterning device, which can be referred to as a mask or a reticle, can be used to generate a circuit pattern corresponding to an individual layer of a flat panel display (or other device). This pattern can be transferred onto all or part of the substrate (e.g., a glass plate), by imaging onto a layer of radiation-sensitive material (e.g., resist) provided on the substrate.
Instead of a circuit pattern, the patterning device can be used to generate other patterns, for example a color filter pattern or a matrix of dots. Instead of a mask, the patterning device can comprise a patterning array that comprises an array of individually controllable elements. The pattern can be changed more quickly and for less cost in such a system compared to a mask-based system.
A flat panel display substrate is typically rectangular in shape. Lithographic apparatus designed to expose a substrate of this type can provide an exposure region that covers a full width of the rectangular substrate, or covers a portion of the width (for example half of the width). The substrate can be scanned underneath the exposure region, while the mask or reticle is synchronously scanned through a beam. In this way, the pattern is transferred to the substrate. If the exposure region covers the full width of the substrate then exposure can be completed with a single scan. If the exposure region covers, for example, half of the width of the substrate, then the substrate can be moved transversely after the first scan, and a further scan is typically performed to expose the remainder of the substrate.
Where an array of individually controllable elements is used as a patterning device, some form of conversion tool or “datapath” is needed to translate a requested dose pattern to a control signal suitable for actuating elements of the array at appropriate times. For example, where the array of individually controllable elements comprises a mirror array, the voltages (defining “setpoints”) will be chosen so as to cause individual mirrors or groups of mirrors to tilt in such a way as to deflect an appropriate portion of incident radiation through the projection system.
Where a desired dose pattern comprises uniform regions or edges, rounding errors arising from quantization of a data stream defining setpoints for the elements of the array of individually controllable elements can lead to a reduction in dose uniformity and/or critical dimension uniformity (the “critical dimension” or “CD” referring to the size of the smallest printable feature).
Therefore, what is needed is a system and method for providing a datapath architecture that reduces the impact of quantization noise arising from digitization of a data stream representing the desired dose pattern.